PROJECT SUMMARY/ABSTRACT HIV risk-reduction interventions traditionally have emphasized individual-centered behavioral prevention approaches. Despite their success, the HIV/AIDS epidemic has not come to a halt, especially not among African Americans, a group that is disproportionately impacted. Structural interventions, which tend to be multilevel, are less common even though structural factors often create vulnerable populations and sustain an environment that is supportive of continued engagement in HIV risk behaviors. In the proposed study, we will investigate how individuals interact with and impact their neighborhood environments. Specifically, we focus on the link between the individual and neighborhood context and the role of structural and environmental factors. We propose a multilevel, longitudinal design and the specific aims are: (1) to investigate the relationships between neighborhood context, neighborhood perceptions, and individual characteristics, and HIV sexual risk-taking and the link between this risk-taking and HIV status; (2) to examine the association between neighborhood context, neighborhood perceptions, individual characteristics, and injection drug use related HIV risk-taking and this risk-taking and HIV status; and (3) to identify the spatial patterns of HIV risk-taking and to investigate neighborhood and individual-level characteristics associated with these spatial patterns. The guiding conceptual model builds on social disorganization theory. Recruitment uses targeted sampling strategies across 50 census block groups, with varied characteristics, and which serve as a proxy for neighborhoods. Our pilot data show these to vary according to key characteristics. In addition, we will explore the local context in which the respondents move. The study sample will consist of 1,500 African American women and men. Comparisons will be drawn based on drug use status, gender, and among the men, sexual orientation. The project comprises distinct data sources, namely: individual interviews, individual HIV status, systematic observations, data from the 2000 U.S. Census, and part 1 crime, drug arrests, and alcohol outlet data. Interviews will be conducted at three time points: baseline and 6 and 12 month follow-up. Systematic observations and a review of crime, drug arrests and alcohol outlet data will occur at baseline and at 12 month follow-up. The analytical approach combines longitudinal multilevel analyses and spatial mapping. The study has theoretical and research significance as its findings may provide useful information for structural interventions, targeting neighborhood structural and environmental factors, that support existing and new HIV prevention approaches. By incorporating partners such as policy-makers, urban planners, economists, legal experts and the wider research community, the public health response to HIV will be enhanced.